Is it better to exchange cash, withdraw THB from the ATM, or use credit cards (when it's an option)?

Returning after many years and am perplexed with how to deal with money. I used to just withdraw from the ATM, but apparently one must be careful about fees.

Which money option should plan for?

I'm pretty sure travelers' cheques are right out, yeah? That was the case in previous decades, but they were the only way to go back in the late 1900's.